Pneumatic tire, a tread band, and a tread block comprising a sipe, and a lamella plate for the manufacture thereof

ABSTRACT

A pneumatic tire is provided with sipes, at least some of which have an open top end to the surface of the tread block. An intersection of the sipe with a surface that is geometrically congruent and parallel with the surface of the tread block and arranged a depth apart from the surface of the tread block into the tread block forms a curved line. A first sipe is shaped in such a way, that at all depths (d) within a range from the open top of the first sipe to a first transition depth, the curved line includes at least one deflection point having an inner corner that has a radius of curvature under 0.3 mm. A lamella plate for manufacturing the pneumatic tire, the tread band, or the tread block. Use of the lamella plate for manufacturing a tread block, a tread band, or a pneumatic tire.

TECHNICAL FIELD

The present application relates to a pneumatic tire or a tread bandhaving tread blocks, and being provided in the tread blocks with sipes,more particularly to an improved shape of a sipe being capable ofproviding better traction of the tire. The present application alsorelates to a lamella plate that is used in the manufacturing process ofa pneumatic tire for making said sipe. The present application alsorelates to the use of said lamella plate for manufacturing a tire or atread band. The present application further relates to a method formanufacturing a lamella plate according to the application.

BACKGROUND

A tread of a known pneumatic tyre is indicated in FIG. 1. A pneumatictire is known to include a tread band having a tread which hascircumferential and transversal grooves 1 on its outer surface, saidgrooves defining a number of protruding parts, such as ribs, shouldersand tread blocks. The tread is meant for a rolling contact against aground surface, such as road. The grooves 1 are meant for draining waterand/or slush that is possibly located on the ground surface away fromthe tread, so that the contact between the tread and the ground surfaceis as good and consistent as possible. Certain types of tires such aswinter tires are provided in the tread with a number of sipes 11 atvarious angles with respect to a motion direction of the tire. The sipes11 not only serve a better tire-ground contact in the rain, but alsoimprove traction, braking and lateral stability on snow by trapping snowas well as providing more gripping edges. The sipes also make the rubbermaterial to deform more easily, in effect making the tire appear softer.This also improves friction.

An example of a sipe 11 in use today is shown in FIG. 1, wherein the topview of the sipe 11 shows a waved line which swings back and forth inthe longitudinal direction of the sipe one or more cycles, with two ormore bent points 12. In between two sipes 11, lamellas 13 are arranged.Lamella plates 33 used in the manufacturing process of a pneumatic tirefor making said kinds of sipes 11 are, for example, shown in FIG. 3a andFIG. 3b . The manufacturing process of said lamella plates 33 is bybending a flat plate into a desired shape with bent points 32.

SUMMARY

An object of the application is to improve the properties of a pneumatictire provided with lamellas and sipes in the tread block so thatlamellas can work more efficiently in the sense of improved gripping,improved stability because of the more efficient locking of the lamella.

It is also an object of the application to provide a lamella plate thatis able to make the sipe according to the present application, whichlamella plate is easy to make so that the cost and time of manufacturinga tire can be reduced.

An embodiment of the application is a tread block 200 (see FIGS. 9 and12 a). Such a tread block 200 may be a tread block 200 of a tire 90 or atread block of a tread band 100, which can be used to form a tread of atire, as indicated in FIGS. 12a and 12b . A preform of a tire 92 can becoated with the tread band 100 to form the tire 90 having the tread withtread blocks 200. Such a tread block 200 is provided with sipes 21, andcan be used as part of a tread band 100 or as part of a tread of a tire90. At least some of the sipes 21 have an open top end (TOP, see FIGS.1, 2 c, 8, 10 a, 12 a) to the surface of the tread block 200, a bottomlocated in the tread block, a first side wall 26 a and a second sidewall 26 b (see FIG. 2a ) curved in the lengthwise direction of the sipe21. The shape of a first sipe 21 of the sipes 21 defines, at each depthd of the first sipe 21, a curved line that is the intersection of thefirst sipe 21 with a surface (107 a, 107 b; see FIGS. 2a and 10b ) thatis geometrically congruent with the surface of the tread block 200,parallel thereto, and located the depth d apart from the open top TOP.At least the first sipe 21 of the sipes 21 of the tread block 200 isshaped in such a way, that at all depths within a range from the opentop TOP of the first sipe 21 to a first transition depth d1, the curvedline 210 comprises at least one deflection point 22 a having an innercorner 220 a, which has a radius of curvature under 0.3 mm, preferablyunder 0.25 mm, and more preferably from 0 to 0.2 mm. The firsttransition depth d1 may be e.g. at least 0.3 mm, at least 0.5 mm or atleast 1.0 mm. The first transition depth d1 may be e.g. from 0.3 mm to 6mm, from 0.5 mm to 6 mm or from 1.0 mm 6 mm.

A pneumatic tire 90 includes a tread that is meant for a rolling contactagainst a ground surface, said tread having a cylindrical shape 971(FIG. 9) with a first radius r1, the tread comprising tread blocks 200provided with sipes 21, at least some of the sipes having an open topend (TOP, FIG. 1, 2 c, 8, 9) to the surface of the tread block, a bottomlocated in the tread block, a first side wall 26 a and a second sidewall 26 b curved in the lengthwise direction of the sipe. Anintersection of at least one of the sipes with a surface of a cylinder972 that is coaxial with the tire and has a second radius r2 forms acurved line 210. Thus, the depth d at which the curved line 210 isobserved, is the difference between the first radius r1 and the secondradius r2. In an embodiment, the side walls 26 a, 26 b have surfacesgeometrically congruent to each other. This improves the locking of theadjacent lamellas on the tire.

In a pneumatic tire 90 according to an embodiment of the application, atleast a first sipe 21 of the sipes 21 is shaped in such a way, that atall depths within a range from the open top TOP of the first sipe 21 toa first transition depth d1, the curved line 210 comprises at least onedeflection point 22 a having an inner corner 220 a that has a radius ofcurvature under 0.3 mm, preferably under 0.25 mm, and more preferablyfrom 0 to 0.2 mm. The first transition depth d1 may be at least 0.3 mm,e.g. at least 0.5 mm, or at least 1 mm, such as from 0.3 to 6 mm, from0.5 to 6 mm or from 1.0 to 6 mm. In an embodiment, the at least onedeflection point 22 a has a deflection angle DA, which is less than 90degrees, preferably less than 75 degrees. In one example, the deflectionangle may be 90 degrees or more.

At a certain depth, greater than a second transition depth d2, thecurved line 210 may comprise such bending points 22 b that have an innerrounded corner 220 b, of which radius of curvature is at least 0.3 mm,preferably at least 0.5 mm (see FIG. 2b ). In one example, the secondtransition depth d2 is greater than the first transition depth d1. Inone example, the second transition depth d2 is at least 0.5 mm greaterthan the first transition depth d1. In an embodiment, at a certain depthd greater than the second transition depth d2, the curved line 210comprises only such bending points 22 b that have an inner roundedcorner 220 b, of which radius of curvature is at least 0.3 mm,preferably at least 0.5 mm.

In one example of the pneumatic tire according to the application, thebottom of the first sipe 21 has an uneven or curved surface, whereby thedepth measured from the surface of the tread block 200 to the bottom ofthe first sipe 21 at a first primary point is different from the depthmeasured from the surface of the tread block to the bottom of the sipe21 at another, second primary, point. The deeper of these locations maybe arranged closer to a center of the sipe than the shallower of theselocations.

In one example of the pneumatic tire the first side wall 26 a of a sipe21 comprises a projection or a recession and the second side wall 26 bof the sipe 21 comprises a geometrically congruent recession orprojection, respectively. In this way, the first and second side walls(26 a, 26 b) form a locking element configured to lock the first andsecond side walls (26 a, 26 b) of the sipe to each other in use.

In one example of the pneumatic tire according to the application, thefirst side wall 26 a of the first sipe 21 and the second side wall 26 bof the first sipe 21 may comprise at least two planes (P1, P2; FIG. 8)which form an angle with each other in the depth-wise direction of thesipe in such a way that the intersection of these planes (P1, P2)extends in a direction that forms an angle of at least 15 degrees withthe normal of the surface of the tread block 200. The angle between thedirection and the normal of the surface of the tread block may be e.g.at least 45 degree or at least 60 degrees.

In one example of the pneumatic tire according to the application, thefirst side wall 26 a of the first sipe 21 and the second side wall 26 bof the first sipe 21 may comprise at least two planes (P1, P2) whichform an angle with each other in the depth-wise direction of the sipe insuch a way that the intersection of these planes (P1, P2) extends in adirection of the surface of the tread of the tire.

In one example of the pneumatic tire according to the application, thefirst side wall 26 a of the first sipe 21 and the second side wall 26 bof the first sipe 21 may be configured in such a way that at a givendepth d

-   -   at a first secondary point 68 a (FIG. 6), the curved line 210        propagates in a first direction, the first secondary point 68 a        defining a first tangential plane having the first secondary        point, the first direction and the direction of the depth,    -   at a second secondary point 68 b, the curved line 210 propagates        in a second direction that is parallel to the first direction or        forms an angle of at most 30 degrees with the first direction,        the second secondary point defining a second tangential plane        having the second secondary point, the second direction and the        direction of the depth, and    -   the first or the second side wall comprises a protrusion 69 in        between the first secondary point and the second secondary        point, wherein the protrusion protrudes to the same direction        from the first tangential plane and the second tangential plane.

In yet one example of the pneumatic tire according to the application,in the first sipe 21,

-   -   the curved line 210 comprises at least three deflection points        in between the first secondary point 68 a and the second        secondary point 68 b;

preferably

-   -   the curved line 210 comprises at least four deflection points in        between the first secondary point 68 a and the second secondary        point 68 b;

more preferably

-   -   the curved line 210 comprises at least four deflection points in        between the first secondary point 68 a and the second secondary        point 68 b and    -   at least one of the deflection points has a deflection angle of        less than 85 degrees.

In an embodiment, the maximum depth of the first sipe is from 4 mm to 10mm. In an embodiment, the minimum depth of the first sipe is from 1 mmto 3 mm. In an embodiment, the depth increases continuously from zero tothe maximum depth. In an embodiment, the maximum width of the first sipeis at most 3 mm or at most 2 mm; such as from 0.2 mm 3 mm or from 0.2 mmto 2 mm. In an embodiment, the length of the first sipe is from 4 mm to10 cm, such as from 1 cm to 10 cm. As is evident, the tire may comprisealso other sipes, of which length, width, and depth may vary accordingto the tread pattern. For example, FIGS. 1a and 10a indicate sipeshaving different lengths.

The tire 90 can be seen as a tire comprising the aforementioned treadblock 200. What has been said about the sipes of the tire 90 applies tothe sipes of the tread block 200. The tire 90 can be seen as a tirecomprising the aforementioned tread band 100. What has been said aboutthe sipes of the tire 90 applies to the sipes of the tread band 100.

A tire 90 can be made e.g. in a tire mould having lamella plates forforming the first sipe 21 and the other sipes 21.

In the alternative, a tread of a tire 90 can be made by applying a treadband 100 onto a preform of a tire 92 (see FIGS. 12a and 12b ). The treadband 100 can be sold e.g. as a planar object, optionally in roll-form.In a tread band 100 according to an embodiment of the application, saidtread band including a tread that is meant for a rolling contact againsta ground surface, at least a first sipe of the sipes 21 is shaped insuch a way, that at all depths within a range from the open top TOP ofthe first sipe to a first transition depth d1, the curved line 210comprises at least one deflection point 22 a having an inner corner 220a, which has a radius of curvature under 0.3 mm, preferably under 0.25mm, and more preferably from 0 to 0.2 mm. As for the values of the firsttransition depth d1, the aforementioned values apply. Here the curvedline 210 refers to the cross-section of the first sipe 21 with a surface(107 a, 107 b) that is geometrically congruent with the surface of thetread band 100, parallel thereto, and located a depth d apart from theopen top TOP. Moreover, the depth is the distance between the open topend TOP of the first sipe 21 and the intersection of the sipe with asurface that is geometrically congruent with the surface of the treadband 100.

In an embodiment, at a certain depth, greater than a second transitiondepth d2, the curved line 210 comprises such bending points 22 b thathave an inner rounded corner 220 b, of which radius of curvature is atleast 0.3 mm, preferably at least 0.5 mm. In one example, the secondtransition depth d2 is greater than the first transition depth d1. Inone example, the second transition depth d2 is at least 0.5 mm greaterthan the first transition depth d1. In one example, at a depth greaterthan the second transition depth d2, the curved line 210 comprises onlysuch bending points 22 b that have an inner rounded corner 220 b, ofwhich radius of curvature is at least 0.3 mm, preferably at least 0.5mm. The at least one deflection point 22 a has a deflection angle DA,which is less than 90 degrees, preferably less than 85 degrees or lessthan 75 degrees. In one example, the deflection angle may be 90 degreesor more.

In an embodiment, the side walls 26 a, 26 b of the sipe of the treadband 100 are geometrically congruent to each other. This improves thelocking of the adjacent lamellas on the tire.

In one example of the tread band 100 according to the application, thebottom of the first sipe may have an uneven or curved surface, wherebythe depth measured from the surface of the tread block to the bottom ofthe first sipe at a first primary point is different from the depthmeasured from the surface of the tread block to the bottom of the sipeat a second primary point.

In one example of the tread band 100 according to the application, inthe first sipe, the first side wall 26 a and the second side wall 26 bmay comprise at least two planes which form an angle with each other inthe depth-wise direction of the sipe in such a way that the intersectionof these planes extends in a direction of the surface of the tread block200.

In one example of the tread band 100 according to the application, inthe first sipe, the first side wall and the second side wall may beconfigured in such a way that for a given depth

-   -   at a first secondary point, the curved line 210 propagates in a        first direction, the first secondary point defining a first        tangential plane having the first secondary point, the first        direction, and the direction of the depth,    -   at a second secondary point, the curved line 210 propagates in a        second direction, that is parallel to the first direction or        forms an angle of at most 30 degrees with the first direction,        the second secondary point defining a second tangential plane        having the second secondary point, the second direction, and the        direction of the depth, and    -   the first or the second side wall comprises a protrusion in        between the first secondary point and the second secondary        point, wherein the protrusion protrudes to the same direction        from the first tangential plane and the second tangential plane.

In yet one example of the tread band 100 according to the application,in the first sipe,

-   -   the curved line 210 comprises at least three deflection points        in between the first secondary point and the second secondary        point;    -   preferably    -   the curved line 210 comprises at least four deflection points in        between the first secondary point and the second secondary        point;    -   more preferably    -   the curved line 210 comprises at least four deflection points in        between the first secondary point and the second secondary point        and    -   at least one of the deflection points has a deflection angle of        less than 85 degrees.

Suitable measures for the sipe 21 of the tread block 100 are the same asthose recited above for the sipes 21 of the tire 90 and/or tread block200.

The tread band 100 can be seen as a tread band comprising theaforementioned tread block 200. The tire 90 can be seen as a tirecomprising the aforementioned tread band 100. As indicated above, theproperties of the first sipe 21, as indicated above, apply to treadblock 200, tread band 100 and tire 90.

According to an embodiment of the present application, a lamella plate43, 53, 63, 73, 83 (see FIGS. 2c, 4a, 4b , 5, 6, 7 a, 7 b, and 8) foruse in the manufacturing process of a pneumatic tire 90, a tread band100, or a tread block 200 according to an embodiment the presentapplication, is configured to form such sipes 21 as discussed above. Bymeans of the lamella plate 43, 53, 63, 73, 83, a sipe 21 is formed inthe tread block 200 e.g. of a tread band 100 or a tyre 90. The lamellaplate has a bottom surface 44, 54, 64, 74, 84, a top surface 45, 55, 75,85 located apart from the bottom surface 44, 54, 64, 74, 84 in adirection of height h of the lamella plate 43, 53, 63, 73, 83. Thelamella plate has a first side wall 46 a, 56 a, 66 a, 76 a, 86 a and asecond side wall 46 b, 56 b, 66 b, 76 b, 86 b curved in a lengthwisedirection L of the plate 43, 53, 63, 73, 83, wherein the lengthwisedirection L is perpendicular to the height h. The side walls may havesurfaces geometrically congruent to each other. A cross section of thelamella plate 43, 53, 63, 73, 83 with a plane P that has a surfacenormal that is parallel to the height h of the lamella plate 43, 53, 63,73, 83 forms a curved line 110 (see FIG. 4a ). In an embodiment, at eachheight within a range from a surface height hs to a first transitionheight h1, the curved line 110 comprises at least one deflection point42, 52, 62, 72, 82, having an inner corner 420, 520, 620, 720, 820 a,which has a radius of curvature under 0.3 mm, preferably under 0.2 mm,and more preferably from 0 to 0.2 mm, wherein the height is the distancebetween the top surface and the cross sectional plane P. Herein theheight is measured from the top surface 44, 54, 64, 74, 84 of thelamella plate 43, 53, 63, 73, 83 towards the plane P. Duringmanufacturing, the lamella plate 43, 53, 63, 73, 83 may be inserted intoa tread bock 200 in such a way that a surface height hs of the lamellaplate is arranged at the surface level of the tread block.

According to some examples of lamella plates 73, 83 of the presentapplication, the difference between said first transition height h1 andsaid surface height hs may be at least 0.3 mm, 0.5 mm or at least 1.0mm, such as from 0.3 mm to 6 mm, from 0.5 mm to 6 mm, or from 1.0 to 3mm.

In an embodiment, at a certain height h greater than a second transitionheight h2, the curved line 110 comprises such bends 720 b, 820 b, ofwhich radius of curvature is at least 0.3 mm or at least 0.5 mm. In anembodiment, at a height h greater than a second transition height h2,the curved line 110 comprises only such bends 720 b, 820 b, of whichradius of curvature is at least 0.3 mm or at least 0.5 mm. In oneexample, the at least one deflection point 72, 82 has a deflectionangle, which is less than 90 degrees, preferably less than 75 degrees.In one example, the deflection angle may be 90 degrees or more.

In some examples of the lamella plates 43, 53, 63, 73, 83 according tothe application, the top surface 45, 55, 75, 85 of the lamella plate maybe uneven or curved, whereby the height measured from the bottom surface44, 54, 64, 74, 84 to the top surface 45, 55, 75, 85 of the lamellaplate at a first primary point O1 is different from the height measuredfrom the bottom surface 44, 54, 64, 74, 84 to the top surface 45, 55,75, 85 of the lamella plate at a second primary point O2 (see FIG. 4a ).The height h of the lamella plate at a central part thereof may begreater than the height at a boundary area thereof.

In one example, the a first side of the lamella plate comprises aprojection or a recession and the second side of the lamella platecomprises a geometrically congruent recession or projection,respectively. In this way, the side of the lamella plate are configuredto form a locking element configured to lock the first and second sidewalls of the sipe to each other in use.

In one example of the of the lamella plates 73, 83 according to theapplication, the first side wall 76 a, 86 a and the second side wall 76b, 86 b may comprise at least two planes P1, P2 (FIG. 8) which form anangle with each other in the height-wise direction of the lamella platein such a way that the intersection of these planes extends in adirection that forms an angle of at least 15 degrees with the directionof height of the lamella plate. The intersection of these planes mayextends in a direction that forms an angle of at least 45 degrees or atleast 60 degrees with the direction of height of the lamella plate.

In some examples of the lamella plates 73, 83 according to theapplication, the first side wall 76 a, 86 a and the second side wall 76b, 86 b may comprise at least two planes P1, P2 which form an angle witheach other in the height-wise direction of the lamella plate in such away that the intersection of these planes extends in a direction of thetop surface of the lamella plate (FIG. 8).

In one example of the lamella plate 53, 63 according to the application(see e.g. FIG. 6), the first side wall 56 a, 66 a and the second sidewall 56 b, 66 b may be configured in such a way that for a given height

-   -   at a first secondary point 58 a, 68 a, the line propagates in a        first direction dir1, the first secondary point defining a first        tangential plane having the first secondary point, the first        direction, and the direction of the height,    -   at a second secondary point 58 b, 68 b, the line propagates in a        second direction dir2 that is parallel to the first direction or        forms an angle of at most 30 degrees with the first direction,        the second secondary point defining a second tangential plane        having the second secondary point, the second direction, and the        direction of the height, and    -   the first or the second side wall comprises a protrusion 59, 69        in between the first secondary point 58 a, 68 a and the second        secondary point 58 b, 68 b, wherein the protrusion 59, 69        protrudes to the same direction from the first tangential plane        and the second tangential plane.

In yet one example of the lamella plate 53, 63 according to theapplication,

-   -   the curved line 110 comprises at least three deflection points        52, 62 in between the first secondary point and the second        secondary point;    -   preferably    -   the curved line 110 comprises at least four deflection points        52, 62 in between the first secondary point and the second        secondary point;    -   more preferably    -   the curved line 110 comprises at least four deflection points        52, 62 in between the first secondary point and the second        secondary point and    -   at least one of the deflection points 52, 62, has a deflection        angle of less than 90 degrees, less than 85 degrees, or less        than 75 degrees.

In an embodiment, the minimum height of the lamella plate is at least0.3 mm, such as at least 0.6 mm, e.g. at least 1 mm. In an embodiment,the maximum width of the lamella plate is at most 3 mm or at most 2 mm;such as from 0.2 mm 3 mm or from 0.2 mm to 2 mm. In an embodiment, thelength of the lamella plate is from 4 mm to 10 cm, such as from 1 cm to10 cm. As is evident, an arrangement of lamella plates is configured toform at least some of the sipes of the tire. The dimensions of thelamella plates of the arrangement of lamella plates may vary accordingto the needs, as indicated above for the corresponding sipes. For anarrangement of lamella plates comprises a first lamella plate and a sendlamella plate, wherein the length of the second lamella plate is greaterthe length of the first lamella plate.

The lamella plate according to an embodiment of the applicationcomprises metal; preferably the lamella plate consists of a metal or ametal alloy.

The lamella plate can be used to manufacture at least one of a treadblock 200, a tread band 100, or a tire 90.

A method for manufacturing a lamella plate according to an embodiment ofthe application comprises removing material from a preform for thelamella plate. Thus, the lamella plate may be machined from the preform.In the alternative (or in addition) such a method could comprise addingmaterial to a preform for the lamella plate. Adding material may includee.g. use of adhesives and/or use of 3D printing techniques. In this way,the sharp corners are possible to be achieved. In an embodiment, thelamella plate is not bent, but is only manufactured by adding and/orremoving material. Naturally, in an embodiment, the plate may also bebent; however sharp corners may not be obtained solely by bending.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a part of a tread of a conventional pneumatic tire;

FIG. 2a shows a close view of examples of sipes according to the presentapplication at a depth below a first transition depth;

FIG. 2b shows a close view of examples of sipes according to anembodiment of the present application at a depth greater than a secondtransition depth;

FIG. 2c shows a sipe as manufactured by the lamella plate of FIG. 4 a;

FIGS. 3a and 3b show conventional lamella plates;

FIG. 4a shows an example of a lamella plate according to the presentapplication;

FIG. 4b shows a top view of the lamella plate shown in FIG. 4 a;

FIG. 5 shows another example of lamella plate according to anembodiment;

FIG. 6 shows a top view of another example of lamella plate, which has asimilar shape as the one shown in FIG. 5, according to an embodiment;

FIGS. 7a and 7b show an example of lamella plate according to anembodiment;

FIG. 8 shows a sipe having been made by the lamella plate of FIGS. 7aand 7 b;

FIG. 9 shows, in a perspective view, a tire 90 and a co-axial anco-centric cylinder 97 intersecting with a sipe 21;

FIGS. 10a and 10b show a, in a perspective view and side view, a treadband on a tire and surfaces 107 a and 107 b that are geometricallycongruent and parallel with the surface of the tread block 200;

FIGS. 11a 1 to 11 a 3 show a part of a tread block with sipes in a firstconfiguration according to an embodiment,

FIGS. 11b 1 to 11 b 3 show a part of a tread block with sipes in asecond configuration according to an embodiment,

FIG. 12a shows a tread band; and

FIG. 12b shows the application of a tread band on a preform of a tire toform a tire.

DETAILED DESCRIPTION

FIG. 9 shows a tire 90 having a tread. The tread may be patterned to thetire using a suitable tool by moulding, or the tread may have been madeby applying a tread band 100 onto a preform of a tire 92 (FIGS. 12a and12b ). The tire tread comprises tread blocks 200 with sipes 21. Thefunction of the sipes 21 has been discussed above in the sectionbackground. The shape of the sipes 21 have a technical effect on howwell the sipes function for their purpose. FIGS. 10a and 10b show, in aperspective view and side view, a tread band 100 on a tyre 90 and twosurfaces 107 a, 107 b that are geometrically congruent and parallel withthe surface of the tread block 200. In FIGS. 10a and 10b only a fewsipes 21 are illustrated for the sake of illustrative clarity. Thesurface 107 a defines the curved line 210 at a first depth d01 (suchlines 210 are indicated e.g. in FIGS. 10a , 9 and 2 a). The surface 107b defines the curved line 210 at a first depth d02. Such depths d01 andd02 may give rise e.g. to the curved lines 210 a and 210 b of FIG. 8. Atread block 200 comprises rubber, such as synthetic rubber or naturalrubber. A tire 90 typically comprises a reinforcing belt structure,plies, sidewalls, and beads. Beads are configured to be fitted on awheel of a vehicle.

Referring to FIG. 9, the tire 90 includes a tread, said tread having acylindrical shape 971 with a first radius r1. The tread comprises treadblocks 200 provided with sipes 21. At least some of the sipes have anopen top end TOP (see FIGS. 1, 2 c, and 8) to the surface of the treadblock 200 and a bottom BOT (FIG. 8) located in the tread block. Thus,the sipes 21 have a first side wall 26 a and a second side wall 26 b(see FIG. 2a ) curved in the lengthwise direction of the sipe 21. Theintersection of at least one of the sipes 21 with a surface of acylinder 972 that is coaxial with the tire and has a second radius r2forms the curved line 210 at a depth d, wherein the depth d is thedifference between the first radius r1 and the second radius r2 (seeFIG. 9). In this way, the shape of the curved line 210 may depend on thedepth at which the sipe is observed. Moreover, as the tire 90 wears,deeper portions of the sipe become exposed on the surface of the treadblock 200. Referring to FIGS. 9, 10 a, 10 b, 2 a, and 2 b, according toan embodiment, at least one of the sipes 21 is shaped in such a way,that at all depths within a range from the open top of the sipe to afirst transition depth d1, the curved line 210 defined by the congruentside walls comprises at least one deflection point 22 a having a sharpinner corner 220 a. This corresponds to a new, unworn tire 90. Asindicated above, when the tire 90 wears, the appearance of the sipe maychange.

In connection with the specification of the present application, theterm “sharp” refers to a deflection point 22 a of the curved line 210,which deflection point 22 a has an inner corner 220 a with a smallradius of curvature (see FIG. 2a ). According to one example of theapplication, the radius of curvature of the sharp inner corner 220 a maybe under 0.3 mm. According to another example of the application, theradius of curvature of the sharp inner corner 220 a may be under 0.25mm. According to yet other examples of the application, the radius ofcurvature may be from 0 to 0.2 mm. The sharp inner corner 220 a may beso sharp that with a naked eye the deflection point 22 a looks like across point of two lines, such as two straight lines or two curves withmuch larger radius of curvature (e.g. at least 1 cm). In other words, inan embodiment, no rounding of the inner corner 220 a can be observed bythe naked eye. It is noted, that when the curved line 210 has adeflection point 22 a with a sharp inner corner 220 a, the correspondingouter corner of the lamella 23, which forms the side of the sipe, isalso sharp.

Correspondingly, the curved line 210 may comprise such an outer corner232 a that the sipe 21 itself, at that point, has a sharp inner corner230 a. What has been said above about the sharpness of the inner corner220 a of the curved line 210 applies equally to the a sharp inner corner230 a of the sipe 21.

It has been found that when the inner corner is sharp in theaforementioned meaning, referring to the inner corner 220 a of thecurved line 210 and/or the inner corner 230 a of the sipe 21, the gripof the tire tread improves a lot. Most likely such a sharp part of thetire bites firmly to surface, such as the road or ground. In particular,when the inner corner 220 a of the curved line 210 is sharp, the outercorner of the lamella 23 is also sharp. Such a sharp outer corner of thelamella 23 bites firmly to surface. In addition, thanks to the sharpedges, lamellas 23 (i.e. the part of the tyre in between the sipes 21)can work more efficiently in the sense of improved gripping and improvedstability, because of the more efficient locking of the lamella to eachother.

In an embodiment, the first transition depth is at least 6 mm. In suchan embodiment, the sipe may have a sharp corner substantially the wholelife of a tyre, provided that the tire is configured to wear 6 mm duringuse. In an embodiment, the tire comprises a groove 1 having a groovedepth dG; and the first transition depth d1 is at least dG-dGR, i.e. atleast the groove depth dG subtracted by a remaining grove depth dGR.Here the remaining grove depth dGR refers to the remaining groove depthof a tire that has worn to the extent that it is no longer safe (or evenlegal) to use it. The remaining groove depth may be e.g. at least 2 mm,such as 2 mm, 3 mm or 4 mm. The groove depth of a new tire may be e.g.at least 6 mm, such as 6 mm, 8 mm, or 10 mm. The groove 1 is left inbetween two tread blocks 200. Specific examples of the pairs (dG; dGR)include (6 mm; 2 mm), (8 mm; 2 mm), (10 mm; 2 mm), (6 mm; 3 mm), (8 mm;3 mm), (10 mm; 3 mm), (6 mm; 4 mm), (8 mm; 4 mm), and (10 mm; 4 mm).Other groove depths dG and first transition depths d1 may be appliedaccording to needs.

In an embodiment, the side walls 26 a, 26 b of the sipe 21 have surfacesthat are geometrically congruent to each other. Such congruent surfacesimprove the locking of the adjacent lamellas 23 to each other duringdriving.

In connection with the specification of the present application, theterm “congruent” is used to describe objects having the same shape andsize, or objects of which one has the same shape and size as the mirrorimage of the other. For example, side walls that have surfacesgeometrically congruent to each other are two opposing side walls havingthe same shape and size in a three-dimensional manner. Moreover, theside wall 26 a of a sipe 21 is formed by a lamella plate; whereby theside wall 26 a is geometrically congruent to a part of a side of thecorresponding lamella plate. Furthermore, the surface, of whichintersection with the sipe 21 defines the line 210 has the same shape asthe surface of the tread block, whereby this intersecting surface isalso congruent with the surface of the tread block.

FIG. 2a shows a close view of some examples of sipes 21 according to thepresent application. Specifically, FIG. 2a shows an intersection of thesipes 21 with a surface of a cylinder 972 that is coaxial with the tire90 at a certain depth d, which is less than a first transition depth d1.The depth d may be zero, whereby FIG. 2a may show the shape of the sipes21 of the open top TOP (cf. FIGS. 2c and 8). As can be seen in FIG. 2a ,the curved line 210 and/or the sipe 21 defined by the two side walls 26a and 26 b, include sharp corners 220 a and 230 a in the aforementionedmeaning. The transition depths d1 and d2 are best illustrated in FIG. 8.Values for the first transition depth d1 as have been recited above. Upto the first transition depth d1, a curved line 210 or a sipe 21comprises a sharp corner 220 a, 230 a in the aforementioned meaning. Oneof the effects brought by this configuration is to improve grip also forsomewhat worn tires. The first transition depth may be e.g. at least 6mm, whereby a lamella 23 has a sharp corner throughout the service lifeof a tire.

The inner corner 220 a of the curved line 210 defines also a deflectionangle DA, as indicated in FIG. 2a . In one example the deflection angleDA may be less than 90 degrees, preferably less than 85 degrees. Inanother example, the deflection angle DA may be less than 75 degrees.One of the effects brought by this configuration is to improve grip. Insome examples, it is also possible that the deflection angle is 90degrees or more. Examples include an angle DA of less than 150 degreesor less than 120 degrees.

Such a sipe 21 can be manufactured by a lamella plate 43, 53, 63, 73,83. Examples of lamella plates are shown in FIGS. 4a , 5, and 7 a. Sucha lamella plate 43, 53, 63, 73, 83 is inserted into the tread block 200,whereby the lamella plate forms a sipe 21 to the tread block such thatthe shape of the sipe 21 matches the shape of the lamella plate 43, 53,63, 73, 83. In particular, the top surface 45, 55, 75, 85 of the lamellaplate is inserted into the tread block to form the bottom BOT of thesipe 21. As indicated in FIGS. 5 and 7 a lamella plate may compriseholes 51, 71. The function of the holes is to enable the flow of rubberfrom one side of the lamella plate to the other side thereof. Enablingthe flow is beneficial, when the sipes comprise sharp corners in theaforementioned sense. However, a lamella plate without such holes mayalso suffice, as indicated in FIG. 4a . During manufacturing, thelamella plate 43, 53, 63, 73, 83 may be inserted into a tread bock 200in such a way that a surface height hs of the lamella plate is arrangedat the surface of the tread block. Thus, the surface height hs of thelamella plate corresponds to the top TOP of the sipe. At the TOP, thedepth d of the sipe is zero. An example of a surface height hs is shownin FIG. 7b ; and a corresponding sipe 21 together with its open top TOPis shown in FIG. 8. The surface height hs may be zero.

FIGS. 4a, 4b , 5, 6, 7 a, and 7 b show examples of lamella plates 43,53, 63, 73, 83 according to an embodiment. With such lamella plates 43,53, 63, 73, 83 the sipes 21 with sharp corners according to someembodiments of the present application can be made. As a mold piecehaving a positive volume, a part of the lamella plate 43, 53, 63, 73, 83creates in the tire 90 or tread band 100 an empty space, i.e. the sipe21, corresponding to the shape of the lamella plate. The lamella plate43, 53, 63, 73, 83 can be made for instance by (at least) an additiveprocess (e.g. 3D printing and/or using adhesive) and/or a removingprocess (e.g. machining) in the shape illustrated in FIGS. 4a, 4b , 5,6, 7 a, and 7 b.

As can be seen in FIGS. 4a, 4b , 5, 6, 7 a, and 7 b, the top view of thelamella plates 43, 53, 63, 73, 83 also has sharp corners. That is, thecurved line 110, which is formed by the intersection of the lamellaplate 43, 53, 63, 73, 83 and a plane P that has a surface normal that isparallel to the height h of the lamella plate (see FIG. 4a ), comprisesat least one sharp inner corner, as defined above. In addition oralternatively, the lamella plate itself comprises a sharp inner corner.This is in contrast to the conventional lamella plates 33 as shown inFIGS. 3a and 3b , which are obtainable by bending a metal plate only toa reasonably large radii of curvature.

Such a lamella plate 43, 53, 63, 73, 83 may be used for manufacturing atread block 200, a tread band 100, or a tire 90. The lamella plate maybe applied in the tread block 200, a tread band 100, or a tire 90 suchthat the height h of the plate is parallel to the depth of the sipe. Inthe alternative, the lamella plate may be applied at an angle (i.e. theheight of the lamella plate forming an angle with the radial directionof the tire and/or surface normal of the tread block).

In the examples as shown in FIGS. 4a and 5, the side walls 46 a, 46 b,56 a, 56 b of the lamella plates 43, 53 have several flat surfaces thatinclude the direction of the height h of the lamella plate. In suchexamples, the transition height in these figures is large, whereby thecurved line 110 defined by the side walls 46 a, 46 b, 56 a, 56 b hassharp corners all the way up to the top of the lamella plate 43, 53.

Also, it can be seen in FIGS. 4a, 4b , 5, 6, 7 a, and 7 b that the topsurface 45, 55, 75, 85 of the lamella plate may by uneven or curved,whereby the height measured from the bottom surface 44, 54, 74, 84 tothe top surface 45, 55, 75, 85 of the lamella plate at a first primarypoint O1 is different from the height measured from the bottom surface44, 54, 74, 84 to the top surface 45, 55, 75, 85 of the lamella plate atanother, second primary point O2. One of the effects brought by thisconfiguration is to improve resistance to tearing stress of the tire inbetween the neighboring sipes. Another effect brought by thisconfiguration is to support the lamellas and the tread block comprisingthe lamella against transverse forces. For example, having a sipe deeperin the central part than in a boundary area (or both boundary areas)will increase the transverse stiffness of the tread block and thelamella. In an embodiment, the height of the lamella plate at the firstprimary point O1 is less than the height of the lamella plate at the atthe second primary point O2 and the second primary point O2 is locatedcloser to a center of the lamella plate than the first primary point O1.

As shown in the FIG. 11a 1, sipes 21 according to one embodiment of thepresent application may be in a zigzag configuration. When a force F,which is a lateral force to a tire, applies from a first direction, thetread block is deformed in such a way that the stressed part of thetread block is moved by the force F to have its side walls partiallyattached to parts of the side walls of the neighboring parts of thetread block, side parts of the side walls being perpendicular to thedirect of applied force F, as shown in FIG. 11a 2. The deformation ofthe tread block is limited by the resistance of the neighboring parts,so that the lateral grip of the tire tread is improved. However, whenthe force F is applied from an opposite direction, the deformation ofthe tread block is larger, as shown in FIG. 11a 3. Therefore, thelateral grip of the tire tread may be weaker in one side than the otherside.

In order to further improve the grip, an embodiment further providesanother configuration of lamella plate and a corresponding sipe 21. Inthe example related to a lamella plate, as shown in FIGS. 5 and 6, thefirst side wall 56 a, 66 a and the second side wall 56 b, 66 b may beconfigured in such a way that

-   -   at a first secondary point 58 a, 68 a, the curved line 110        propagates in a first direction dirt the first secondary point        58 a, 68 a defining a first tangential plane (plane1, FIG. 6)        having the first secondary point 58 a, 68 a, the first direction        dirt and the direction of the height h of the lamella plate,    -   at a second secondary point 58 b, 68 b, the curved line 110        propagates in a second direction dir2 that is parallel to the        first direction dir1 or forms an angle of at most 30 degrees        with the first direction dir1, the second secondary point 58 b,        68 b defining a second tangential plane (plane2, FIG. 6) having        the second secondary point 58 b, 68 b, the second direction        dir2, and the direction of the height h of the lamella plate,        and    -   the first or the second side wall 56 a, 66 a, 56 b, 66 b        comprises a protrusion 59, 69 in between the first secondary        point 58 a, 68 a and the second secondary point 58 b, 68 b,        wherein the protrusion 59, 69 protrudes to the same direction        from the first tangential plane and the second tangential plane.

In FIG. 6, a lamella 23 formed by the lamella plate extends from thefirst or the second tangential plane (plane1, plane2) towards the secondor the first tangential plane, respectively (plane2, plane1), andextends as protrusion on also on the other side of the second or thefirst tangential plane, respectively (plane2, plane1).

In the example as shown in FIG. 5, the curved line 110 comprises fourdeflection points 52, and the deflection points 52 have an acutedeflection angle; in the example as shown in FIG. 6, the line comprisesfive deflection points 62, and some of the deflection points 62 have anacute deflection. The acute deflection angle DA may be e.g. less than 90degrees, less than 85 degrees, or less than 75 degrees.

A corresponding sipe 21 of a tire 90 or tread band 100, indicated inFIG. 11b 1, is shaped in such a way that

-   -   at a first secondary point, the curved line 210 propagates in a        first direction dir1, the first secondary point defining a first        tangential plane (plane1, FIG. 11b 1) having the first secondary        point, the first direction dirt and a direction of a sidewall 26        a, 26 b of the sipe 21 at the first secondary point, the        direction of the sidewall 26 a, 26 b being perpendicular to the        first direction dir1,    -   at a second secondary point, the curved line 210 propagates in a        second direction dir2 that is parallel to the first direction        dir1 or forms an angle of at most 30 degrees with the first        direction dir1, the second secondary point defining a second        tangential plane (plane2, FIG. 11b 1) having the second        secondary point, the second direction dir2, and a direction of a        sidewall 26 a, 26 b of the sipe 21 at the second secondary        point, the direction of the sidewall 26 a, 26 b being        perpendicular to the second direction dir2, and    -   the first or the second side wall 26 a, 26 b comprises a        protrusion 59, 69 in between the first secondary point and the        second secondary point, wherein the protrusion 59, 69 protrudes        to the same direction from the first tangential plane and the        second tangential plane.

It is noted that the first and second tangential planes may comprise theradial direction of the tire 90, if the sipes are formed by insertingthe lamella plate into the tire such that the height h is parallel to aradial direction of the tire. In such a case, the aforementioned adirection of a sidewall 26 a, 26 b of the sipe 21, the direction of thesidewall 26 a, 26 b being perpendicular to the first (or second)direction at the first (or second) secondary point would be parallel tothe depth of the sipe 21, i.e. the radial direction; or in case of atread block, parallel to the normal of the surface of the tread block.

Referring to FIG. 6, in an embodiment, a lamella 23 limiting a sipe 21extends from the first or the second tangential plane (plane1, plane2)towards the second or the first tangential plane, respectively (plane2,plane1), and extends as protrusion on also on the other side of thesecond or the first tangential plane, respectively (plane2, plane1).Such sipes 21 are shown in FIGS. 11b 1 to 11 b 3. In the example asshown in FIGS. 11b 1 to 11 b 3, the curved line 210 comprises fivedeflection points, in between the first secondary point and the secondsecondary point. Some of the deflection points have an acute deflectionangle. The acute deflection angle DA may be less than 85 degrees.

FIGS. 11b 1 to 11 b 3 show an example of tread block having the sipesmanufactured with the lamella plates having the configuration as definedabove. As can be seen in the FIGS. 11b 2 and 11 b 2, the deformation ofthe tread block is equally well limited when the force F applies eitherof the longitudinal directions of the sipe. Therefore the grip of thetire tread as well as the handling of the tire are improved in manydirections. Moreover, It has been found that when a deflection angle isless than 90 degrees, such as less than 85 degrees or less than 75degrees, and the corresponding inner corner is sharp in theaforementioned meaning, the grip of the tire tread improves a lot. Mostlikely such a sharp part of the tire bites firmly to ground.

In the examples as shown in FIGS. 7a and 7b , the side walls 76 a, 76 b,86 a, 86 b of the lamella plates 73, 83 have bent surfaces in theheight-wise direction h. In other words, the surface comprises at leasttwo planes P1, P2 which form an angle with each other. The angle may bearound 90 degrees, so that a stairs-like configuration is formed. Theangle may also be more the 90 degrees, so that a slope-likeconfiguration is formed. The at least two planes P1, P2 which form anangle with each other in the height-wise direction of the lamella platein such a way that the intersection of these planes extends in adirection of the top surface of the lamella plate. One of the effectsbrought by this configuration is to provide shape-locking of the sidewalls of the sipes. As is evident, the sipe 21 formed with such alamella plate, as indicated in FIG. 8, also comprises the aforementionedat least two planes P1, P2. These planes P1, P2 form an angle with eachother in the depth-wise direction of the sipe 21 in such a way that theintersection of these planes extends in a direction that is notperpendicular to the direction of the tread surface of the tire 90 orthe tread band 100. Examples of the such angles have been given above.

Such shapes are examples of a more general shape-locking of neighbouringlamella to each other in use. In an embodiment, the first side wall 26 aof the sipe 21 comprises a projection or a recession and the second sidewall 26 b of the sipe 21 comprises a geometrically congruent recessionor projection, respectively. In this way, the first and second sidewalls 26 a, 26 b form a locking element configured to lock the first andsecond side walls 26 a, 26 b to each other.

In the examples as shown in FIGS. 7a and 7b , in between the surfaceheight hs and the first transition height h1 the curved line 110 linedefined by the side walls has sharp corners 720 a, 820 a. The lamellaplate may comprise at least one sharp corner in the aforementionedmeaning at all heights from the aforementioned surface height hs to thefirst transition height h1. The first transition height h1 may be atleast 0.3 mm, at least 0.5 mm, or at least 1.0 mm greater than thesurface height hs, such as from 0.3 mm to 6 mm, from 0.5 mm to 6 mm, orfrom 1.0 mm to 6 mm greater than the surface height hs. As indicated inFIG. 8, the corresponding curved line 210 a of the sipe 21 comprises asharp inner corner 220 a, when the curved line 210 a is defined for adepth of at most the first transition depth d1.

Referring to FIGS. 7a and 7b , at a certain height, greater than asecond transition height h2, the curved line 110 may comprise such bendswhich form rounded corners 720 b, 820 b. The radius of curvature of therounded corners may be at least 0.3 mm, preferably at least 0.5 mm. Thishas the effect that at the bottom of a corresponding sipe, thecorresponding sipe is has at least some rounded corners, which are lessvulnerable to tearing. In an embodiment, at a height greater than asecond transition height h2, the curved line 110 comprises only suchbends which form rounded corners 720 b, 820 b. As indicated in FIG. 8,the corresponding curved line 210 b of the sipe 21 only comprisesrounded corners when the curved line 210 b is defined for a depth of atleast the second transition depth d2.

One of the effects brought by this configuration is to improve tearresistance of the sipes 21. This improves the reliability of the tire,in particular the reliability of the sipes 21, because the tearingstresses acting on the tread near sipes have less locations toconcentrate in. Should the sipes have sharp corners also at the bottom,tearing stress would concentrate precisely on the sharp corners, andcould tear off the sipes. The second transition depth d2 is greater thanor equal to the first transition depth d1.

Correspondingly, the first sipe 21 of a tyre is arranged such that atall depths from a second transition depth d2 to the bottom of the firstsipe 21, the curved line 210 (i.e. 210 b) only comprises such bendingpoints that have an inner rounded corner, of which radius of curvatureis at least 0.3 mm, preferably at least 0.5 mm. Moreover, in anembodiment the second transition depth d2 is greater than the firsttransition depth d1. In an embodiment, the second transition depth d2 isat least 0.5 mm, at least 0.7 mm, or at least 1.0 mm greater than thefirst transition depth d1. Having a reasonable large difference inbetween the transition depths (d1, d2) improves the tear resistance alsoin between the transition depths.

The tear resistance is also somewhat better, if the first sipe 21 isshaped in such a way, that at all depths from a second transition depthd2 to the bottom of the first sipe 21, the curved line 210 comprisessuch a bending point 22 b that has an inner rounded corner 220 b, ofwhich radius of curvature is at least 0.3 mm, preferably at least 0.5mm.

In an embodiment, all the corners of curved line (curved line 110 of thelamella plate or curved line 210 of the sipe) are formed such that theangle of each inner corner is less than 90, less than 85, or less than75. This further improves the grip, since such acute lamellas have beenobserved to improve the grip. Until now, such sipes and lamella plateshave not been manufactured, since such structures are hard for form bybending.

It is also noted that even if a pneumatic tyre is, at least soon aftervulcanization, elastic and soft, after aging e.g. for several months,the material of the tyre becomes harder and more brittle. Thus, therounding of the corners at the bottom of the sipe takes also intoaccount the long term reliability problems related to aging of material.In addition, in typical use, the sharp corners at the top of the sipemay wear off in typically use before the material becomes hard.

In an embodiment, the lamella plate and/or the sipe is formed in such away that the width of the lamella plate and/or the sipe is formed suchthat the width of the sipe is greater at the bottom than at the top(i.e. the open end of the sipe). Referring to FIG. 7b , a lamella platemay be formed such that the width W2 at the top surface 85 is greaterthan the width W1 of the lamella plate at the surface height hs.Referring to FIG. 8, a sipe 21 may be formed such that the width W2 atthe bottom of the sipe is greater than the width W1 of the sipe at thetop.

In such a structure, as the tyre wears, the sipes 21 become wider. Thus,the lamellas 23 in between the sipes 21 can deform more before thelamella 23 makes a contact with an adjacent lamella 23. In this way, asthe tyre wears, the siped tread blocks become, in effect, softer. At thesame time, however, the material of the tyre hardens due to aging. Ineffect, such a shape of a sipe ensures that the tyre properties remainreasonably constant in use, even if the tyre wears and the materialthereof ages. This is particularly beneficial, when a sipe comprises asharp edge as discussed above.

The width W2 at the bottom of the sipe 21 (or top of lamella plate) maybe e.g. at least 20% greater or at least 30% greater than the width W1at the top of the sipe 21 (or at the surface height hs of the lamellaplate). For example, W1 may be from 0.1 mm to 2 mm, while W2 may be from0.5 mm to 3 mm.

It is also possible to form the sipe and/or the lamella plate in such away that the shape of the curved line (110 or the lamella plate and/or210 of the sipe) changes significantly as the tyre wears.

Lamella plates according to some embodiments of the present applicationcan be manufactured by for example by an additive manufacturingtechnology, such as 3D printing. In the alternative or in addition, asubtractive manufacturing technology, such as machining, can be used inthe process of manufacturing a lamella plate. The technique(s) areapplied in such a way that so that a corner is sharp up to the firsttransition height h1; and optionally so that the corners start to becomemore rounded only after the first transition height h1.

The sipes according to the embodiments of the present application areparticularly feasible in winter tires. Such a winter tire may comprisestuds 300 (see FIG. 10a ), or the tire may be free from studs.

The invention claimed is:
 1. A tread block for a tread of a pneumatictire or for a tread band for a pneumatic tire, the tread blockcomprising: a plurality of sipes, at least some of the plurality ofsipes each having an open top end to the surface of the tread block, abottom located in the tread block, and a first side wall and a secondside wall curved in the lengthwise direction of the sipe, anintersection of the sipe with a surface that is geometrically congruentand parallel with the surface of the tread block and arranged a depthapart from the surface of the tread block into the tread block forming acurved line, wherein at least a first sipe of the plurality of sipes isshaped such that, at all depths within a range from the open top end ofthe first sipe to a first transition depth of at least 0.3 mm, thecurved line comprises at least one deflection point having an innercorner that has a radius of curvature under 0.3 mm, and the first sipeis shaped such that, at all depths from a second transition depth to thebottom of the first sipe, the curved line comprises a bending point thathas an inner rounded corner, a radius of curvature of the inner roundedcorner being at least 0.3 mm, the second transition depth being greaterthan the first transition depth.
 2. A tread band for a tread pneumatictire, the tread band comprising the tread block of claim
 1. 3. Apneumatic tire having comprising: a tread configured for rolling contactagainst a ground surface, said tread having a cylindrical shape, thetread comprising tread blocks of claim
 1. 4. The tread block accordingto claim 1, wherein said at least one deflection point has a deflectionangle that is less than 90 degrees.
 5. The tread block according toclaim 4, wherein said deflection angle is less than 75 degrees.
 6. Thetread block according to claim 1, wherein the bottom of the first sipehas an uneven or curved surface, whereby the depth of the first sipemeasured from the surface of the tread block to the bottom of the firstsipe at a first primary point is different from the depth of the firstsipe measured from the surface of the tread block to the bottom of thesipe at a second primary point.
 7. The tread block according to claim 6,wherein the depth of the first sipe at the first primary point is lessthan the depth of the first sipe at the second primary point and thesecond primary point is located closer to a center of the first sipethan the first primary point.
 8. The tread block according to claim 1,wherein the first side wall comprises a projection or a recession andthe second side wall comprises a geometrically congruent recession orprojection, respectively, whereby the first and second side walls form alocking element configured to lock the first and second side walls toeach other.
 9. The tread block according to claim 8, wherein the firstside wall and the second side wall comprise at least two planes whichform an angle with each other in the depth-wise direction of the firstsipe such that the intersection of the planes extends in a directionthat forms an angle of at least 15 degrees with the normal of thesurface of the tread block.
 10. The tread block according to claim 1,wherein the first side wall and the second side wall are configured suchthat, for a given depth at a first secondary point, the curved linepropagates in a first direction, the first secondary point defining afirst tangential plane including the first secondary point, the firstdirection, and a direction of a sidewall of the first sipe, thedirection of the sidewall being perpendicular to the first direction, ata second secondary point, the curved line propagates in a seconddirection that is parallel to the first direction or forms an angle ofat most 30 degrees with the first direction, the second secondary pointdefining a second tangential plane including second secondary point, thesecond direction and a direction of a sidewall of the first sipe, thedirection of the sidewall being perpendicular to the second direction,and the first or the second side wall comprises a protrusion in betweenthe first secondary point and the second secondary point, the protrusionprotruding to the same direction from the first tangential plane and thesecond tangential plane.
 11. The tread block according claim 10, whereinthe curved line comprises at least three deflection points in betweenthe first secondary point and the second secondary point.
 12. The treadblock according to claim 1, wherein the inner corner of the deflectionpoint has a radius of curvature under 0.25 mm.
 13. The tread blockaccording to claim 1, wherein said first transition depth is from 0.3 mmto 6 mm.
 14. The tread block according to claim 1, wherein radius ofcurvature is at least 0.5 mm.
 15. A lamella plate suitable formanufacturing a pneumatic tire, a tread band, or a tread block, thelamella plate being configured to form a sipe in the tread block of thepneumatic tire or the tread band, the lamella plate comprising: a bottomsurface; a top surface located apart from the bottom surface in adirection of height of the lamella plate; and a first side wall and asecond side wall curved in a lengthwise direction of the lamella plate,the lengthwise direction being perpendicular to the height and across-section of the lamella plate with a plane that has a surfacenormal that is parallel to the height of the lamella plate and isdisposed at a height from the bottom surface forming a curved line,wherein, at all heights within a range from a surface height to a firsttransition height of at least 0.3 mm, as measured from the bottomsurface of the lamella plate, the curved line comprises at least onedeflection point having an inner corner that has a radius of curvatureunder 0.3 mm, and at all heights from a second transition height to thebottom surface of the lamella plate, the curved line comprises a bendingpoint that has an inner rounded corner, a radius of curvature of theinner rounded corner being at least 0.3 mm, the second transition heightbeing greater than the first transition height.
 16. The lamella plateaccording to claim 15, wherein the lamella plate comprises metal. 17.The lamella plate according to claim 15, wherein the height of thelamella plate is at least 4 mm, and the first transition height is atleast 0.3 mm greater than the surface height.